Roger Mortimer, 1st earl of March, (born 1287?—died Nov. 29, 1330, Tyburn, near London, Eng.), lover of the English king Edward II’s queen, Isabella of France, with whom he contrived Edward’s deposition and murder (1327). For three years thereafter he was virtual king of England during the minority of Edward III.

The descendant of Norman knights who had accompanied William the Conqueror, he inherited wealthy family estates and fortunes, principally in Wales and Ireland, and in 1304 became 8th Baron of Wigmore on the death of his father, the 7th baron. He devoted the early years of his majority to obtaining effective control of his Irish lordships against his wife’s kinsmen, the Lacys, who summoned to their aid Edward Bruce, brother of King Robert I of Scotland, when he was fighting to become king of Ireland. In 1316 Mortimer was defeated at Kells and withdrew to England, but afterward, as King Edward II’s lieutenant in Ireland (November 1316), he was largely instrumental in overcoming Bruce and in driving the Lacys from Meath.

In 1317 he was associated with the Earl of Pembroke’s “middle party” in English politics; but distrust of the Despensers (seeDespenser, Hugh Le and Hugh Le) drove him, in common with other marcher lords, into opposition and violent conflict with the Despensers in South Wales in 1321. But, receiving no help from Edward II’s other enemies, Roger and his uncle Roger Mortimer of Chirk made their submission in January 1322. Imprisoned in the Tower of London, Roger escaped in 1323 and fled to France, where in 1325 he was joined by Queen Isabella, who became his mistress. The exiles invaded England in September 1326; the fall of the Despensers was followed by the deposition of Edward II and his subsequent murder (1327), in which Mortimer was deeply implicated.

Thereafter, as the queen’s paramour, Mortimer virtually ruled England. He used his position to further his own ends. Created Earl of March in October 1328, he secured for himself the lordships of Denbigh, Oswestry, and Clun, formerly belonging to the Earl of Arundel; the marcher lordships of the Mortimers of Chirk; and Montgomery, granted to him by the queen. His insatiableavarice, his arrogance, and his unpopular policy toward Scotland aroused against Mortimer a general revulsion among his fellow barons, and in October 1330 the young king Edward III, at the instigation of Henry of Lancaster, had him seized at Nottingham and conveyed to the Tower. Condemned for crimes declared to be notorious by his peers in Parliament, he was hanged at Tyburn as a traitor, and his estates were forfeited to the crown.